CN1192830A - Adaptive despreader - Google Patents
Adaptive despreader Download PDFInfo
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- CN1192830A CN1192830A CN96196064A CN96196064A CN1192830A CN 1192830 A CN1192830 A CN 1192830A CN 96196064 A CN96196064 A CN 96196064A CN 96196064 A CN96196064 A CN 96196064A CN 1192830 A CN1192830 A CN 1192830A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
- H04B1/711—Interference-related aspects the interference being multi-path interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7097—Interference-related aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03012—Arrangements for removing intersymbol interference operating in the time domain
- H04L25/03019—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception
- H04L25/03038—Arrangements for removing intersymbol interference operating in the time domain adaptive, i.e. capable of adjustment during data reception with a non-recursive structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/0335—Arrangements for removing intersymbol interference characterised by the type of transmission
- H04L2025/03375—Passband transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03433—Arrangements for removing intersymbol interference characterised by equaliser structure
- H04L2025/03439—Fixed structures
- H04L2025/03445—Time domain
- H04L2025/03471—Tapped delay lines
- H04L2025/03477—Tapped delay lines not time-recursive
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L2025/03592—Adaptation methods
- H04L2025/03598—Algorithms
- H04L2025/03611—Iterative algorithms
- H04L2025/03617—Time recursive algorithms
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Abstract
A method and apparatus for adaptively despreading a direct sequence spread spectrum signal. The direct sequence spread spectrum signal is provided to transversal filter (101). The output of filter (101) is despread by despreader (120) to provide a soft symbol determined by symbol estimator (122). The soft symbol is provided to decision circuit (124) which generates an error corrected version of the soft symbol data, referred to as a hard symbol. The value of the hard symbol is subtracted from the soft symbol by subtractor (126) to generate an error symbol. The error symbol is then used to compute tap values of the transversal filter by means of an LMS algorithm employed by tap adapter (103).
Description
Technical field
The present invention relates to a kind of communication system, relate in particular to a kind of novelty through improved method and apparatus, with not telling under the situation of multipath decline, improve the performance of Direct swquence spread spectrum receiver.
Background technology
Developed plurality of communication systems with from the seedbed point to different customer objective ground transmit information signals.Used analog-and digital-two kinds of methods on the communication channel of linked source and user locations, to transmit this category information signal.Digital method has several advantages with respect to analogue technique, comprises the immunity to interference that has for example improved interchannel noise and interference, has increased capacity, by encrypting the fail safe that improves communication.
When being on the communication channel transmit information signals from information source, earlier information signal is converted to the form of transmission effectively that is suitable on channel.The parameter that the conversion of information signal or modulation comprise according to information signal change carrier wave makes the spectrum limitations of the modulated carrier that produces in channel width.At the user place, reproduce the origination message signal according to the form of the modulated carrier that after propagating on the channel, receives.This reproduction utilizes the opposite mode of using with the information source transmitter of modulation treatment to realize usually.
Modulation also helps multiple access technology, promptly simultaneously at a plurality of signals of same channel.Multi-address communication system often comprises a plurality of Remote Interface Units, and they need the gap service of short period, rather than meet the people continuously to communication channel.The system that is designed to one group of subscriber unit is communicated at short notice is called multi-address communication system.
A kind of multi-address communication system of specific type is called spread spectrum system, and in spread spectrum system, the signal extension of used modulation technique handle transmission is on the broadband of communication channel.One type multiple access spread spectrum system is code division multiple access (CDMA) modulating system.Other multi-address communication system technology, for example time division multiple access (TDMA), frequency division multiple access (FDMA) and all be known technology such as AM modulator approaches such as amplitude companded single sidebands.
Yet CDMA has significant advantage on the modulation technique of these multi-address communication systems.The U.S. Patent No. 4 that is called " the spread spectrum multiple access communication system of using satellite or terrestrial repetition station " in name, 901,307 and name be called the U.S. Patent No. 5 of the system and method for signal waveform " in the cdma cellular telephone system produce ", 103, disclosed a kind of CDMA technology of in multi-address communication system, using in 459, this two patent all transfers assignee of the present invention, all is incorporated herein, as a reference.
In the cdma cellular telephone system, identical frequency band is used for the communication of used cell unit.Provide the CDMA waveform characteristic of processing gain also to be used to distinguish the signal that takies same frequency band.And high speed pseudo noise (PN) modulation can make many different propagation paths be separated, as long as path difference exceeds PN chip duration or 1/ bandwidth.If use the PN spreading rate of 1MHz, the multipath modulation is used in the path that then can differ from the path delay in desired path more than the microsecond.1 microsecond path delay difference is corresponding to 1000 feet path distance.The path delay of urban environment surpasses 1 little title usually, has report to reach the 10-20 microsecond in some areas.
In the narrowband modulation system, for example simulation FM modulation of traditional cellular phone system use, the existence of multipath may cause serious fading characteristic.Yet,, can distinguish different paths with demodulation process for the wideband CDMA modulation.Use CDMA to distinguish technology and can not all eliminate the multipath decline, because have the path of delay inequality sometimes less than the minimal path time-delay of particular system.Signal with path delay of this degree can not be distinguished in demodulator.Therefore, wish that system uses some diversity forms, with further minimizing fading effect.
The power of transmitter can be controlled disadvantageous fading effect to a certain extent in the control cdma system.The U.S. Patent No. 5 that is called " method and apparatus of the transmitting power of control cdma cellular mobile telephone system " in name, disclosed a kind of system that distinguishes unit and the control of mobile unit power in 056,109, this patent transfers assignee of the present invention, be incorporated herein, with for referencial use.And, when mobile unit between the cell coverage that has mobile unit communication district unit during the hand-off process when mobile, under switch mode, can reduce the multipath fading effect.Be called in name in the U.S. Patent No. 5,101,501 of " soft handover in the cdma cellular telephone system " and disclosed this handover scheme, this patent has transferred assignee of the present invention, is incorporated herein, with for referencial use.
The existence of multipath can provide path diversity for wideband CDMA system.If have the path delay of two or mulitpath to differ by more than more than 1 microsecond, then can receive these signals independently with two or more receivers.Because these signals show in multipath decline usually separate (being their declines simultaneously usually), so output that can two receivers of diversity combination.Be called in name in the U.S. Patent No. 5,109,390 of " diversity receiver in the cdma cellular telephone system " and disclosed the method and apparatus of realizing this class combination receiver, this patent has transferred assignee of the present invention, is incorporated herein, with for referencial use.
Summary of the invention
The present invention be a kind of novelty through improved method and apparatus, with not telling under the situation of multipath decline, improve the performance of Direct swquence spread spectrum receiver.N.5 the present invention can replace above-mentioned United States Patent (USP), the diversity receiver structure of the Direct swquence spread spectrum receiver of describing in 101,501.The present invention is similar to diversity receiver on function, but it has simple in structure and has improved performance under the situation that can not tell multipath.It also is applicable to the system of high data rate, may be optimal in indoor use.Its novelty is to have added on traditional adaptive equalizer goes to expand and extended operation again.
The multipath propagation of finding in indoor environment in 800 to 2000MHz scopes has quite short time delay expansion usually.The scope of this expansion can be from about 20ns to 300ns, changes with the design and the other factors of size, characteristic and the metope of building.When the time-delay between the multipath assembly during greater than the sequence spreading chip, it is the most effective to be used for the diversity receiver that direct sequence receives in the honeycomb cells external environment.In standardized CDMA design, as above-mentioned U.S. Patent No. 4,901,307 and 5,103, described in 459, be about 800ns during the chip.Mean in the diversity receiver that than time delay expansion length only a restituted signal is useful during the chip.And the multipath that can not tell will cause the Rayleigh fading of a restituted signal output of smooth diversity receiver.Therefore, the diversity receiver gain that can have than long delay can not realize.
The indoor method that must use a kind of processing multi-path signal of novelty of short time delay expansion.The present invention uses a kind of equaliser structure to achieve this end.The objective of the invention is to reduce the intersymbol interference that multipath propagation causes.Use the common tap-weights of using the feedback updated transversal filter of judging based on independent code element of equalizer of classic lowest mean square (LMS) algorithm.The LMS algorithm is estimated the reverse gradient with respect to the error function of tap-weights, and adjusts tap-weights on the direction with respect to the gradient of estimating.Under suitable channel statistics and gain situation, filter converges to the state that can reduce intersymbol interference effectively.The LMS algorithm is widely used, and be because it is simple, be easy to calculate, and it does not need repeating data.Yet, in this application, directly do not use the LMS algorithm, be because direct sequence extension.
In cdma cellular and pcs system, multichannel is not to go up with symbol time unit's (tens microseconds) to introduce intersymbol interference through expansion, but with chip chronomere (tens to hundreds of nanosecond).Therefore, adaptive equalizer of the present invention has the function of Error Feedback between chip and chip.For this reason, must come the data estimator modulation according to error of going spread signal, estimation and the difference between the soft or hard of expanding again by the original pseudo noise sequence judgement of proofreading and correct as tap-weights before being fed.
Typical implementation of the present invention is used for the demodulation pilot frequency channel.Pilot channel is the channel that is used to provide synchronizing information basic time (not load data).The use implementation of pilot channel has detailed description in above-mentioned U.S. Patent No. 5,103,459.The present invention can use in the channel of demodulation out of Memory, and as long as less change.Summary of drawings
By the detailed description below in conjunction with accompanying drawing, it is more obvious that features, objects and advantages of the invention will become, the corresponding parts of identical in the drawings symbolic representation.
Fig. 1 is a block diagram of the present invention.
Embodiments of the present invention
Fig. 1 shows the structure of novel adaptive despreader, and it can balanced broad-band channel.Fig. 1 does not illustrate the down-conversion spread spectrum signal and it is converted to the receiver of Data Base band signal, because this is well-known in this technical field.Adaptive despreader 100 comprises transversal filter 101, lowest mean square (LMS) tap refresh circuit 103 and symbol estimation, remove expansion and expanded circuit 121 again.Adaptive despreader 100 is depicted as by the apportion element to be formed.In exemplary embodiments, adaptive despreader 100 is to realize described function with microprocessor or microcontroller with programming mode.Though Fig. 1 does not illustrate independent timing square frame, should be noted that this clock regularly provides usually in microprocessor or microcontroller, perhaps provide by time source independently.
Transversal filter 101 is finite impulse response (FIR) (FIR) filters, and it receives the data-signal R of expression spread spectrum signal baseband form.Sample R (n) that transversal filter 101 bases receive recently and the sample R (n) that receives previously, R (n-1), R (n-2), R (n-3) and R (n-4) produce filtering signal.Structure shown in Figure 1 has five taps.It is the value through filtering, the sample R (n) that offers adding element 146, R (n-1), R (n-2), R (n-3) and R (n-4) that S (n) is based on five value R that receive (n) and receives previously.Though in exemplary embodiments, shown structure is five tap FIR filters, also can use arbitrarily the tap consistent with performance requirement.
The signal that receives is offered a series of delay cells 102,104,106 and 108.In spread spectrum communication system, the transmission information of smallest pieces is called chip.Each chip has predetermined chip period.Each delay cell 102,104,106 and 108 is the value that equals signal sampling period of chip time-delay that receives.In exemplary embodiments, input sample speed is the less integral multiple of spreading rate.For example, spreading rate is 1.25MHz, and integral multiple can be 4, and respective sample speed is 5MHz.Delay cell 102,104,106 and 108 can utilize the known latch of this technical field or its memory element to realize.
The output of current sample R (n) and each delay cell 102,104,106 and 108 is offered multiplier 110,112,114,116 and 118 respectively.In multiplier 110,112,114,116 and 118, respectively with weighted taps value w1, w2, w3, w4 and w5 are to the sample value weighting, and these weighted taps values are calculated by LMS tap refresh circuit 103 (back description).Each sample value through weighting is offered adder (∑) 146.Adder 146 produces output valve Sn to each sample value addition through weighting.Adder 146 is with the value Sn of spreading rate output through filtering, i.e. value of each chip period.
The output chip Sn of transversal filter 101 is offered symbol estimation, removes expansion and expanded circuit 121 again.Sn offers multiplier 120 the output chip.In multiplier 120, the binary number of the pseudo random sequence that provides with spreading rate through the chip Sn of filtering and pseudo random sequence (PRS) generator 132 of input is multiplied each other.The long-pending symbol estimation device 122 that offers of multiplier 120.Symbol estimation device 122 carries out integration to the output result of multiplier 120 on greater than the code-element period of chip period, go the code element of expanding with generation.Symbol estimation device 122 can be made by the known digital integrator of this technical field.Symbol estimation device 122 can also provide symbol mapped, provides first symbol estimation through the chip value of integration, and its predetermined mapped is mapped to soft code element.Typical mapping is the Hadamard transform mapping.
If expansion is a bipolarity phase shift key (BPSK), then go sequence spreading also should be bi-polar value (±), the same with the sequence spreading that uses on the transmitter.If expansion is quadrature phase shift key (QPSK), then its I and Q component should be bi-polar value usually, and removing sequence spreading is the complex conjugate of the sequence spreading of transmitter use.In exemplary embodiments, PRS generator 132 utilizes shift register to realize, in this technical field, is known to the design and the realization of this shift register.
Go extended operation to produce the low-pass signal component of the data-modulated that occurs in the signal corresponding to original transmitted.Pseudo noise multiplies each other and does not compress the interference at other station, and equally will keep broadband waveform as what describe in detail in the above-mentioned U.S. Patent No. 4,901,307 and 5,103,459.
The output of 122 pairs of adders 146 of symbol estimation device is operated.The sample of 122 pairs of transversal filters 101 of symbol estimation device carries out filtering, perhaps handles, and is created in the estimated value of the modulated symbol of each code-element period emission.Usually, a large amount of chips works to each code element, reflects the bigger ratio of extending bandwidth to data speed.In Fig. 1, the output of this symbol estimation device is designated as " soft code element "
124 pairs of soft code elements of decision circuit are for further processing.The output of decision circuit 124 is complex values, and it is the reconstruct of the modulated symbol of original transmitted.Under the situation of demodulated pilot signal, this code element is by complex representation, for example a 1+0j.Under the situation of demodulated pilot signal, decision circuit 124 is a comparator, and a chip value and a constant through integration that symbol estimation device 122 is provided compare.Decision circuit 124 is used for producing unmodulated pilot tone estimated value.On the other hand, decision circuit 124 can be such as plural circuit such as viterbi decoders, and the channel symbol of coding again is provided, as its last result who judges.
Error waveform is calculated to be poor between soft decision code element that symbol estimation device 122 provides and the hard decision code element that decision circuit 124 provides in adder 146.This plural number error e (n) is expanded with the pseudo random sequence through delay cell 130 time-delays that PRS generator 132 provides in multiplier 128 again.Delay cell 130 can be known latch or memory constitute.
Calculating tap-weights according to the LMS algorithm in LMS tap refresh circuit 103 upgrades.Must use original spread signal sample, rather than modulated symbol.These are different with traditional LMS adaptive equalizer, in traditional equalizer, signal are gone expansion, judge to carry out code element, and expand to be used for tap again and upgrade.
Use according to it, the structure of decision circuit 124 can have different implementations.In exemplary embodiments, the major part of forward link power is exclusively used in expansion rather than unmodulated pilot tone, and the code element of emission is a priori known and is constant.So the output of decision circuit 124 is irrelevant at all with the signal that receives, and is a constant simply, for example 1+0j.Therefore, soft code element is the short term average of despreader output, and symbol error is poor between these short term average and the constant desired value.
The code element judgement is based on a plurality of chip value.Therefore, they are obsolete, until comprise their last chip a period of time afterwards.Because this time-delay, R (n) delays time to the received signal before offering LMS tap refresh circuit 103, must delay time to pseudo random sequence before offering multiplier 128.130 pairs of pseudo random sequences of delay cell are delayed time, and delay cell 176 R (n) to the received signal provides time-delay.The length of these time-delays is at least a data code element.If use the information of Viterbi decoding side, then time-delay will be several code elements, at this moment since last code element judge lag behind reception be at least decoder block length (truncationlength).
The time alignment that is brought into channel samples is fed back decision errors in time-delay shown in Figure 1.Therefore their duration is about a code element.General code-element period is 52.1 μ s on forward link, is 208.3 μ s on reverse link.Extended code each chip of delaying time only needs to remember 2 bits, or 128 and 512 bits.Therefore, with 8 times of mistakes take a sample 4 bits and when being used for I and Q sample of signal will need 8192 and 32768 bits respectively.
At code check is that modulation of ρ, m unit and data rate are in the system of R, and code-element period is provided by following
T
xymb＝ρ·log
2m/R (1)
So the time-delay to sample can followingly be calculated:
T
symb·f
chip＝ρ·log
2m·f
chip·S/R (2)
Wherein S is the mistake sampling rate to signal.
One can calculate the needed tap number of transversal filter according to total time-delay span of multi-path signal.Therefore if the time-delay span was set to for 200 nanoseconds, then under the sampling rate of 20Mhz, can following calculating tap number:
200ns20MHz+1 〉=5 taps (3)
Be necessary like this.
The success of this method depends on adaptive speed, and it should be enough fast, to follow the tracks of the short term variations that moves the obvious multipath that causes mainly due to mobile phone.For handheld unit, can estimate that the speed that changes with 1800MHz and 3m/s (6.7mph) is about 2fv/c=36 null value (null)/second, perhaps about 28ms between null value.This just requires auto-adaptive time should be not more than the hundreds of microsecond, and this method could success.When automobile speed, about 10 times of this time decreased, or be about 2.8ms.
Fixed gain shown in the handle be multiply by error signal in multiplier 134 before turning back to LMS tap refresh circuit 103.This gain must be through suitably selecting, if this is because too little, may cause convergence slowly, may cause instability too greatly.
LMS tap refresh circuit 103 receives the weighted error signal of multiplier 134 and the sample through time-delay of delay cell 176.The sample through time-delay of delay unit 176 is offered a series of delay cells 168,170,172 and 174.Each delay cell 168,170,172 with 174 as described the same with 108, the additional sample cycle of the sample time-delay that receives about delay cell 102,104,16.
The output of delay cell 176,168,170,172 and 174 is offered multiplier 158,160,162,164 and 166 respectively.The output of multiplier 158,160,162,164 and 166 is offered the first input end of adder 148,150,152,154 and 156 respectively.The output of adding element 148,150,152,154 and 156 is offered delay unit 136,138,140,142 and 144.The adder 148,150,152,154 and 56 second input are single sample time-delay output of each adder 136,138,140,142 and 144.Delay unit 136,138,140,142 and 144 is sample cycle of input sample time-delay.The output of delay unit 136,138,140,142 and 144 is offered transversal filter 101 as values of tap, offer multiplier 110,112,114,116 and 118 respectively.
This structure is simpler than diversity receiver.Only need a demodulator, in diversity receiver, need a plurality of demodulators on the contrary.It does not also need to search for multi-path signal and for multi-path signal distributes restitution element, this is because tap position is fixed with fixed intervals.Because there is not dynamic assignment, so the loss that does not distribute error to cause.Owing to a soft decision output is only arranged, so do not need deflection.When the more complicated degree, can use more a plurality of taps, can obtain better diversity gain.
Description to preferred embodiment can make these those skilled in the art make or use the present invention above.Obviously, the various changes to these embodiment are that significantly the General Principle of Xian Dinging can be applied to other embodiment and need not creativity here for these those skilled in the art.Therefore, the embodiment shown in the present invention is not limited to here, but should be according to the novel feature the widest corresponding to scope of the principle that discloses here.
Claims (23)
1, a kind of adaptive despreader comprises:
Laterally filter receives the sample of importing, and according to one group of adaptive-filtering values of tap described input sample is carried out filtering, and to produce the chip value through filtering, wherein, described self adaptation values of tap is upgraded according to expanding error signal again;
Remove expanding unit, receive described chip value, described chip through filtering is gone expansion,, produce second estimating code element according to predetermined judgement form so that first estimating code element to be provided according to the Direct swquence spread spectrum form through filtering;
Error calculating device receives described first estimated signal and described second estimated signal, produces error signal according to described first estimated signal and described second estimated signal;
Expanding unit receives described error signal, according to predetermined extended frequency spectrum form spread-spectrum is expanded described error signal, so that the described error signal of expansion again to be provided.
2, device as claimed in claim 1 is characterized in that, described horizontal filter is finite impulse response (FIR) (FIR) filter.
3, device as claimed in claim 1 is characterized in that, the described expanding unit that goes comprises:
The symbol estimation device produces the first symbol estimation value according to described chip value through filtering; And
Hard decision device produces hard symbol estimation value according to described first symbol estimation value and predetermined hard decision form.
4, device as claimed in claim 3 is characterized in that, described hard decision device comprises comparison circuit.
5, device as claimed in claim 3 is characterized in that, described hard decision device comprises viterbi decoder.
6, device as claimed in claim 3 is characterized in that, the described expanding unit that goes also comprises:
Pseudo-random sequence generator produces pseudo random sequence; And
Multiplier receives described described chip value and the described pseudo random sequence of reception through filtering that multiplies each other, and described chip value through filtering be multiply by described pseudo random sequence, so that product sequence to be provided.
7, device as claimed in claim 1 is characterized in that, described horizontal filter upgrades described values of tap according to lowest mean square (LMS) tap self adaptation form.
8, device as claimed in claim 6 is characterized in that, described symbol estimation device carries out integration to described product sequence, so that sequence spreading to be provided.
9, device as claimed in claim 8 is characterized in that, described symbol estimation device also is mapped to second sequence to the described sequence spreading that goes according to the predetermined mapped form.
10, device as claimed in claim 9 is characterized in that, described mapping format is a Hadamard transform.
11, a kind of method of removing to expand spread spectrum signal adaptively comprises the following step:
Receive the input sample;
According to one group of adaptive-filtering values of tap described input sample is carried out filtering, the chip value through filtering is provided, wherein said self adaptation values of tap is upgraded according to expanding error signal again;
Go to expand described chip value according to the Direct swquence spread spectrum form, first estimating code element is provided through filtering;
Produce second estimating code element according to predetermined judgement form;
Produce error signal according to described first estimated signal and described second estimated signal; And
Expand described error signal according to predetermined spread-spectrum form, the described error signal of expanding again is provided.
12, method as claimed in claim 11 is characterized in that, described filter step comprises carries out finite impulse response (FIR) filtering to described input sample.
13, method as claimed in claim 11 is characterized in that, described step of going to expand described chip value through filtering comprises:
Produce the first symbol estimation value according to described chip value through filtering; And
Produce hard symbol estimation value according to described first symbol estimation value and predetermined hard decision form.
14, method as claimed in claim 13 is characterized in that, the step of the hard symbol estimation value of described generation comprises the described first symbol estimation value and one group of threshold ratio.
15, method as claimed in claim 13 is characterized in that, the described step that produces sign indicating number symbol estimation value comprises carries out Viterbi decoding to the described first symbol estimation value.
16, method as claimed in claim 13 is characterized in that, the described spread step of going also comprises:
Produce pseudo random sequence; And
Described chip value through filtering be multiply by described pseudo random sequence, produce product sequence.
17, method as claimed in claim 11 is characterized in that, also comprises according to lowest mean square (LMS) tap self adaptation form to upgrade described values of tap.
18, method as claimed in claim 16 is characterized in that, describedly goes spread step also to comprise described product sequence to be carried out integration, sequence spreading is provided.
19, method as claimed in claim 18 is characterized in that, describedly goes spread step also to comprise according to the predetermined mapped form the described sequence spreading that goes is mapped to second sequence.
20, method as claimed in claim 19 is characterized in that, described mapping format is a Hadamard transform.
21, a kind of adaptive despreader comprises:
Transversal filter has first input end that receives the input sample and second input that receives the tap updating value, also has an output;
Error Calculator has the input of the output that is couple to described transversal filter and the output of spread-spectrum calculated error signal is provided; And
Tap update calculation device has first input end that is couple on the described Error Calculator output and the output that is couple on the described second transversal filter input.
22, device as claimed in claim 21 is characterized in that, described Error Calculator comprises:
Symbol estimation device with input and output side;
Decision circuit has the input that is couple on the described symbol estimation device output; And
Subtracter has first input end that is couple to described symbol estimation device output and second input that is couple to described decision circuit output, also has an output.
23, device as claimed in claim 22 is characterized in that, described Error Calculator also comprises despreader, and its input is couple to described transversal filter, and its output is couple to the input of described symbol estimation device.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/509,722 US5692006A (en) | 1995-07-31 | 1995-07-31 | Adaptive despreader |
| US08/509,722 | 1995-07-31 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1192830A true CN1192830A (en) | 1998-09-09 |
| CN1091554C CN1091554C (en) | 2002-09-25 |
Family
ID=24027839
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN96196064A Expired - Lifetime CN1091554C (en) | 1995-07-31 | 1996-07-31 | Adaptive despreader |
Country Status (17)
| Country | Link |
|---|---|
| US (1) | US5692006A (en) |
| EP (1) | EP0842568B1 (en) |
| JP (2) | JP3241739B2 (en) |
| KR (1) | KR19990036012A (en) |
| CN (1) | CN1091554C (en) |
| AR (1) | AR003021A1 (en) |
| AT (1) | ATE279814T1 (en) |
| AU (1) | AU6715896A (en) |
| BR (1) | BR9609939A (en) |
| CA (1) | CA2228131A1 (en) |
| DE (1) | DE69633625T2 (en) |
| FI (1) | FI980162A (en) |
| HK (1) | HK1010952A1 (en) |
| MX (1) | MX9800853A (en) |
| TW (1) | TW322667B (en) |
| WO (1) | WO1997005709A1 (en) |
| ZA (1) | ZA966011B (en) |
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1995
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-
1996
- 1996-07-15 ZA ZA966011A patent/ZA966011B/en unknown
- 1996-07-24 AR ARP960103720A patent/AR003021A1/en unknown
- 1996-07-31 AU AU67158/96A patent/AU6715896A/en not_active Abandoned
- 1996-07-31 AT AT96927283T patent/ATE279814T1/en not_active IP Right Cessation
- 1996-07-31 JP JP50787397A patent/JP3241739B2/en not_active Expired - Fee Related
- 1996-07-31 CN CN96196064A patent/CN1091554C/en not_active Expired - Lifetime
- 1996-07-31 KR KR1019980700676A patent/KR19990036012A/en active IP Right Grant
- 1996-07-31 BR BR9609939A patent/BR9609939A/en not_active Application Discontinuation
- 1996-07-31 WO PCT/US1996/012531 patent/WO1997005709A1/en active IP Right Grant
- 1996-07-31 EP EP96927283A patent/EP0842568B1/en not_active Expired - Lifetime
- 1996-07-31 DE DE69633625T patent/DE69633625T2/en not_active Expired - Lifetime
- 1996-07-31 MX MX9800853A patent/MX9800853A/en not_active IP Right Cessation
- 1996-07-31 CA CA002228131A patent/CA2228131A1/en not_active Abandoned
- 1996-08-30 TW TW085110590A patent/TW322667B/zh active
-
1998
- 1998-01-26 FI FI980162A patent/FI980162A/en not_active IP Right Cessation
- 1998-08-19 HK HK98110014A patent/HK1010952A1/en not_active IP Right Cessation
-
2001
- 2001-04-11 JP JP2001112626A patent/JP2001352277A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| EP0842568A1 (en) | 1998-05-20 |
| DE69633625D1 (en) | 2004-11-18 |
| BR9609939A (en) | 1999-06-08 |
| FI980162A (en) | 1998-03-30 |
| ATE279814T1 (en) | 2004-10-15 |
| EP0842568B1 (en) | 2004-10-13 |
| JPH11510343A (en) | 1999-09-07 |
| ZA966011B (en) | 1997-01-31 |
| JP3241739B2 (en) | 2001-12-25 |
| JP2001352277A (en) | 2001-12-21 |
| FI980162A0 (en) | 1998-01-26 |
| TW322667B (en) | 1997-12-11 |
| KR19990036012A (en) | 1999-05-25 |
| WO1997005709A1 (en) | 1997-02-13 |
| MX9800853A (en) | 1998-04-30 |
| AR003021A1 (en) | 1998-05-27 |
| AU6715896A (en) | 1997-02-26 |
| CN1091554C (en) | 2002-09-25 |
| DE69633625T2 (en) | 2005-10-27 |
| HK1010952A1 (en) | 1999-07-02 |
| US5692006A (en) | 1997-11-25 |
| CA2228131A1 (en) | 1997-02-13 |
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